If you're more specific, we may be able to help you sort through some of your issues.
As for the self punching, you know it's a bad coping mechanism. You should choose not to punch yourself. I recommend a mattress or a couch or a pillow as suitable punching targets. It's cliche, but an unsent angry letter can be cathartic. Also don't be afraid to have a good cry if you feel it coming on.
As for dwelling if you're not working on a solution to a tangible problem, there's no need to dwell (you likely will anyway but put in an honest effort to stay focused on other things). For depression in general, it's best to stay productive in my experience. Work on something, perhaps a hobby or a skill.
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Sleepless gliding